This application claims the priority of Korean Patent Application No. 2003-89367, filed on Dec. 10, 2003, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
1. Field of the Invention
The present invention relates to a zoom lens barrel for a camera such as a digital camera, and more particularly, to a zoom lens barrel having a total length which is remarkably reduced.
2. Description of the Related Art
In general, a lens barrel used for a camera such as a digital camera, capable of zooming and having an accommodation function, includes a first lens group, a second lens group, and a third lens group arranged in an optical axis direction from an object to be photographed, and an actuating mechanism to move the lens groups in the optical axis direction. The zoom lens barrel further includes a shutter unit having an opening portion for exposure, a blade capable of adjusting a degree of opening of the opening portion, and an electronic drive source to drive the blade. Recently, it is a trend to make a camera such as a digital camera thinner and smaller.
In a conventional film camera, however, since the opening portion needs to be shielded by closing the blade of the shutter unit to prevent film from being exposed to light when the camera is in a zoom state or in an accommodation state, the shutter unit and the lens groups cannot be overlapped. Accordingly, there is a limit in reducing the total length of the lens barrel so that it is difficult to make the camera thinner and smaller.
In the conventional typical digital camera, since the inner diameter of the opening portion of the shutter unit is less than the outer diameter of a lens frame, the shutter unit and the second lens group cannot be overlapped and the shutter unit is fixed by being separated a predetermined distance from the second lens group. In the accommodation state as in the zoom state, the shutter unit needs to maintain a predetermined distance from the second lens group. Thus, there is a limit in making the camera thinner and smaller by reducing the total length of the lens barrel.
Japanese Patent Publication No. 2003-121720 discloses a structure of a lens barrel of a camera in which the shutter unit is fixed to the first lens group. In the lens barrel, since the inner diameter of the opening portion of the shutter unit is less than the lens frame of the second lens group, even if they are overlapped at their maximum, only a very small portion of a leading end of the second lens group overlaps the opening portion of the shutter unit so that there is a limit in reducing the total length of the lens barrel. Furthermore, in the accommodation state as in the zoom state, since the maximum open size of the blade of the shutter unit remains the same, it is difficult to make the shutter unit and the second lens group completely overlapping each other.